The present invention relates to a projection-type image display apparatus that projects an image onto a screen or the like, and particularly relates to a technique for improving image quality.
A projection-type image display apparatus that projects an image onto a screen or the like is configured to adjust brightness of an image to be projected and improve a contrast performance by providing an diaphragm mechanism to adjust a light ray transmission amount in an illumination system or a projection system (For example, refer to Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2003-241311). Further, there is also employed a method to improve an apparent dynamic contrast by controlling a diaphragm stop of the diaphragm mechanism in conjunction with a picture signal.
Meanwhile, in a projection-type image display apparatus using a liquid crystal device, there arises a problem such as moving image blurring due to a poor response characteristic of liquid crystal, and it is pointed out that a moving image performance is not satisfactory. Accordingly, efforts to improve the moving image performance have been made by increasing a frame frequency for image display or inserting a black signal between frames.
However, when the method of increasing the frame frequency is employed to improve the moving image performance, image switching speed is increased and therefore sometimes it becomes difficult to keep a sufficient time for the response of liquid crystal, and a negative influence is caused in a brightness performance. Further, when the method of inserting the black signal is employed, it is necessary to input the black signal in an earlier timing when the response characteristic of the liquid crystal is poor, and therefore a negative influence is also caused in brightness.